1. Field of the Invention
This invention relates to a multiple point focus detection camera that accomplishes the focusing operation on the basis of focus detection data measured by the specific focus detection area from among multiple focus detection areas.
2. Description of Related Art
Conventionally, a camera endowed with a focus detector establishes a focus detection area 8 in the center of the finder field of vision 9 in the manner shown in FIG. 3. In the focus detection area 8, focus detection is accomplished such that the lens is moved to focus on the subject within the focus detection area 8.
However, when the focus detection area 8 is in the center of the finder field of vision 9 as shown in FIG. 3, and if the primary photographic subject intended by the photographer is not found within the center of the finder field of vision 9, the photographs may be taken when focusing on a subject other than the primary photographic subject.
Therefore, as shown in FIG. 4, multiple focus detection areas 8 are established in the finder field of vision 9, from which a selection is made of a specific area. The camera is constructed so as to focus the lens relative to the photographic subject within the selected area. With such a camera, two methods are known for the selection of an area from the multiple focus detection areas 8. In a first method, one focus detection area from the multiple focus detection areas 8 is selected by the photographer. The lens is then focused on the subject in the selected area. In the second method, the focus is detected in all of the areas of the multiple focus detection area 8, and through the processing of the received focus detection data, a selection is made of an area in which the primary subject exists, thus comprising a method in which the lens is focused on the photographic subject in the selected area. In this instance, as a standard for the selection of the focus detection area, construction may be such that selection is made of a focus detection area in which the distance is closer to the camera. Conventionally, from these two methods, the first method has been called the manual mode, and the second method has been called the automatic mode, cameras being known in which both capabilities are provided, both of them being selectively used by the photographer.
An explanation is provided hereafter of a conventional multiple point focus detection camera that is provided with both a manual mode and an automatic mode.
FIGS. 7 and 8 show an external view of such a conventional camera. With a multiple point focus detection camera there is provided a power switch 3, a release button 4, a display window 5, a mode change button 6, and a command dial 10 arranged on the top of the camera body 1. The area selection lever 7, which is used by the photographer to select the area when operating in the manual mode, is attached to the rear surface of the camera body in FIG. 7 and is attached to the side surface of the lens 2 in FIG. 8.
Next, an explanation will be provided of the operation of a calculation controller or CPU, to determine the point for focusing from focus detection in a multiple point focus detection camera with reference to FIG. 5.
First, in step S201, if the release button 4 is half depressed, then the calculation controller accomplishes focus detection in step S202. Next, the calculation controller determines whether the mode selected in step S203 is the manual mode or the automatic mode. If the automatic mode is selected, the calculation controller moves to step S204, and the focus detection data relevant to the entire focus detection area 8 is detected. In step S205, the calculation controller accomplishes the calculations on the basis of a specified algorithm, wherein a determination is made as to the focus detection area in which the subject exists, the established focus detection area being displayed in the focus detection area (step S206).
Furthermore, in step S207, in order to focus on the subject within the established focus detection area, the calculation controller calculates the amount of drive of the AF (automatic focus) motor required to focus, on the basis of the focus detection data of this area. In step S208, the AF motor is driven by an amount corresponding to the AF motor controller. Finally in step S209, the calculation controller receives the drive of the AF motor, and focusing is accomplished through the movement of the focusing lens in the direction of the optical axis. In step S210, the operation waits for the full depression of the release, and photography is accomplished when the release button has been fully depressed.
In step S203, when the established mode is the manual mode, the calculation controller moves to step S216 and only detects the focus detection data of the focus detection area selected by the area selection lever 7. The calculation controller moves to step S207 and accomplishes both focusing and photography.
With the automatic mode in the conventional arrangement, since the selection of a specific area is automatically accomplished on some basis, occasionally selection will be made of an area in which the photographic subject is different from the primary subject recognized by the photographer. In such an instance, the photographer will have to switch from the automatic mode to the manual mode and again situate the camera and push the release button.
On the other hand, in the manual mode, since selection of the area of the primary subject intended by the photographer is accomplished manually, there is an advantage in that a picture can be taken in accordance with the desired composition of the photographer. However, since focusing is accomplished in a pre-established area, if the photographer forgets that the camera is in the manual mode, there is a possibility that a picture may be taken while focusing on other than the primary subject.
In this manner, with a multiple point focus detection camera provided with a conventional automatic mode and manual mode, there is a need for frequent changing from the manual to the automatic mode, which is time consuming and inefficient.